Measure-set computed tomographic analysis of internal architectures of lumbar disc. Clinical and histologic studies

Measure-set computed tomography (MSCT) scan was performed in 30 adult subjects (17 men and 13 women, mean age 42 years) and eight cadavers (five men and three women, mean age 42 years) to establish prospectively a normal CT pattern of the internal architectures of the lumbar disc. Based on the uniformity or nonuniformity of MSCT composition of the nucleus pulposus (NP) and annulus fibrosus (AF), and also on how well NP was discerned from the surrounding AF, the internal architecture could be categorized into well-defined (WD), intermediate (IM), and ill-defined (ID) types. An age and prevalence study of the categorized disc showed that, with age, the disc undergoes an architectural transformation from WD through IM to ID. In addition, 72.5% of WD-type discs and 72.1% of ID-type discs occurred in the third and fourth decades and in the sixth and seventh decades, respectively, suggesting that the former is a young form with mild degeneration and the latter an old form with advanced degeneration. Fifty-eight percent of WD-type discs and 60.4% of ID-type discs occurred at L1-3 and L4-S1 levels, respectively, regardless of age. This finding suggests the old form tends to occur at the lumbosacral junction, which is the site of maximum weight bearing in humans. The correlation of water content and histologic findings of degeneration with the three categorized disc types in cadavers showed that WD, IM, and ID discs were associated with the largest, intermediary, and least amount of water of NP, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)